No one knows what causes reflex sympathetic dystrophy syndrome (RSDS), also known as complex regional pain syndrome (CRPS), or why it follows an estimated 5 percent of all injuries. The condition is an under-diagnosed and under-treated neurological syndrome characterized by swelling, skin discoloration, stiffness, and intense and chronic burning pain. RSDS affects as many as 6 million Americans; it is most often set off by a relatively minor physical...